U.S. No. 2,696,482 describes an amorphous polyamide derived from bis(4-aminocyclohexyl)methane and isophthalic acid, which is unsuitable for processing in, for example, injection molding because its viscosity is too high.
German 1,795,464 discloses a process for the preparation of amorphous copolyamides from combinations of alkyl-substituted hexamethylenediamines, isophthalic acid and terephthalic acid. These products also have viscosities so high that they are difficult to work.
U.S. No. 3,597,400 describes an amorphous copolyamide derived from bis (4-aminocyclohexyl)methane, hexamethylenediamines, isophthalic acid and terephthalic acid, in which the compositions having high proportions of bis(4-aminocyclohexyl)methane clearly exhibit high melt viscosities and therefore lend themselves poorly to processing, e.g. by injection molding; however, even at low diamine concentrations, viscosities are still sufficiently high that the preparation of large molded parts is difficult.
According to U.S. No. 4,369,305, viscosities below 30,000 poise at 280.degree. C. and a shear value of 10.sup.5 dyn/cm.sup.2 are obtained if a copolyamide composition contains particular proportions of iso- and terephthalic acids, very low proportions of bis(4-aminocyclohexyl)methane in a particular mixture of isomers; viz. at least 59% by weight trans/trans or cis/trans isomers.
U.S. No. 4,536,541 describes an amorphous copolyamide which also includes a small amount of bis(4-aminocyclohexyl)methane isomers and is modified for impact-resistance with a particular ethylene/propylene/diene copolymer (EPDM) activated with succinic acid.
It is known that, if impact-resistant modifiers of this type are worked into polyamides, they considerably increase the melt viscosity (U.S. No. 4,174,538 and German 1,242,606), so that the processing of such polyamides is again made more difficult. By contrast, a reduction of the amount of bis(4-aminocyclohexyl)methane in the amorphous copolyamide has the effect of reducing the retention of form on heating and deteriorates certain mechanical properties; e.g. viscosity and strength.
British 998,439 describes the introduction of modified polyolefins and polyacrylates into linear partially crystalline polyamides to modify impact-resistance. Impact resistance modification using particular reactive copolyolefins is described in detail in German DE-A-2,722,270 for the polyamides PA 6 and PA 66. However, partially-crystalline polyamides have a very low melt viscosity, the increase in viscosity due to the modification causes no problem in processing thermoplastic compositions of this type.
U.S. No. 4,339,555 describes the modification of conventional homopolyamides with particular copolyolefins which contain, in addition, urea derivatives for the improvement of the melt and forming processes.
British 2,170,209 discloses a transparent copolyamide derived from a dicarboxylic acid such as isophthalic acid and a diamine component comprising bis(4-amino-3,5-diethylcyclohexyl)methane as Well as other polyamide-forming components. British Patent Application 86 29928 discloses a similar product, but one in which the principal diamine is bis(4-amino-3-ethyl-5-methylcyclohexyl) methane.